There exist methods for converting lignocellulosic biomass into fermentable C5 and C6 sugars. Several of these methods first produce oligomers of the C5 and C6 sugars, which are then hydrolyzed to form fermentable streams of monomers of C5 and C6 sugars. Problems exist with current methods, including, inter alia, that due to the very short residence times in the reactor there are control issues often lead to unwanted degradation products, such as acids that inhibit fermentation. It would, therefore, be beneficial to develop methods that would be scalable and controllable, that maximize monomer formation, and that minimize the formation of degradation products. The methods and compositions of the present invention are directed toward these, as well as other, important ends.